Flash released a new update to their plugin today. To update, go to System Preferences, select Flash (usually in the bottom row), then select Advanced. In there you will find a button labeled “Check Now” in the Updates section. Click that and follow the prompts and instructions. Once installed, next to the button it should say “Plug-in version 11.7.700.169 is installed.”
Try to install this update as soon as you can to make sure you are protected from the slew of vulnerabilities in the previous version.